Liquid compositions of overbased calcium carboxylate and process for its preparation

ABSTRACT

The present invention relates to light color, shelf-stable liquid compositions of overbased calcium carboxylate soaps and a process for their preparation. The inventive soaps are prepared by neutralizing calcium base in a mixture of two different aliphatic carboxylic acids and carbonating the mixture in the presence of a non-polar hydrocarbon solvent and a polar organic solvent as a promoter under controlled temperature conditions. The overbased calcium carboxylate soaps of the invention contain 20%-90% by weight of C 7  to C 25  saturated carboxylic acids, which are branched on carbon 2, and between 1% and 20% by weight short chain saturated carboxylic acids. These liquid compositions have light colors and excellent heat stability. They can be used as anticorrosion/antirust additives, and paint dryers and stabilizers, in paints, coatings and lubricants, as well as other applications.

FIELD OF THE INVENTION

This invention generally relates generally to liquid compositions ofcalcium carboxylate soaps with a high basicity index, commonly calledoverbased calcium soaps. In particular, this invention relates to lightcolor, shelf-stable liquid compositions of overbased calcium carboxylatesoaps and a process for their preparation. By light color it is meanthaving a clear yellow or amber color, and by shelf-stable is meant beingcapable of storage in a closed container at room temperature for atleast 90 days without suffering visible gelatization, clotting orprecipitation.

BACKGROUND OF THE INVENTION

The preparation of overbased calcium salts of carboxylic acids, alkylphenols, and sulfonic acids are disclosed in the U.S. Pat. Nos.2,616,904; 2,760,970; 2,767,164; 2,798,852; 2,802,816; 3,027,325;3,031,284; 3,342,733; 3,533,975; 3,773,664; and 3,779,922. As describedtherein, the widely used overbased calcium soaps are either salts ofalkylarylsulphonic acids, oleic acid, naphthenic acids, or branchedsaturated oxo-acids of C₇ to C₂₅ hydrocarbons.

U.S. Pat. Nos. 2,865,956; 2,938,828; and 4,100,084 report variousmethods of producing calcium naphthenates. These products often haverelatively slow filtration rates and contain considerable amounts ofsolids, predominantly non-dispersible, agglomerated calcium carbonateparticles which require measures for their removal. The overbasednaphthenates are often dark in color which limits their use inapplications where discoloration is a problem, such as in paints andcoatings. The preparation of these compounds typically involves tworeactions and can be summarized as follows:

1) Preparation of Calcium Naphthenate:2RCO₂H+M(OH)₂→(RCOO)₂M+H₂O2) Overbasing:(RCOO)₂M+XM(OH)₂→(RCOO)₂M_(x)+MCO₃In which:

-   M is a metal-   X ranges from 1 to 10-   R is a hydrocarbyl radical of 15 to 40 carbon atoms.-   Step 2 takes place in the presence of CO₂ gas and a solvent.

The preparation of the overbased salts using alkylarylsulphonic acid isa difficult process. Typically the process involves the reaction thealkylarylsulphonic acid with a metal oxide or hydroxide in a suitablesolvent.

U.S. Pat. No. 4,225,509 teaches an overbased alkaline earth metalhydrocarbyl sulfonate which is made in the presence of carbon dioxide(CO₂) and promoters. The promoters are usually labile hydrogen compoundssuch as phenols, alcohols and amino-alcohols. Products prepared by suchmethod have dark colors and it is difficult for them to reach high metalcontent.

U.S. Pat. No. 4,597,880 discloses a one-step process for preparation ofoverbased calcium sulfonate greases. The essential ingredients include amixture of a liquid carrier, a sulfonic acid, calcium oxide orhydroxide, water-soluble carboxylic acids, preferably an alcohol oralkoxyalcohol of 1 to 8 carbon atoms, and water, wherein the mixture iscarbonated. Calcium soaps from this method of preparation cannot be usedin paint applications because of dark color.

In U.S. Pat. No. 4,824,585, overbased calcium soaps having a basicity ofabout 4 are described which overcome the disadvantages of the knownsoaps and which yield stable and clear solutions in oil. As used aboveand throughout this application, basicity is the total amount of calciumin a product divided by the amount of calcium linked to carboxylic acidcompounds. The products described in this patent are made by carbonationof excess of calcium hydroxide dispersed in a reaction medium containingan oil-soluble organic acid, a hydrocarbon solvent, a low molecularweight alcohol, and mineral oil, followed by filtration of the unreactedmaterials. Carbonation is carried out in the presence of catalysts suchas metal oxides and zinc carboxylates and promoters of higher alcohols,glycols, alky-phenols or amines. These compounds remain in the finishedproduct and the presence of the catalyst and oil in the finished productcan limit its use.

In the U.S. Pat. Nos. 4,824,585, 5,501,807 and 5,830,832, high basicitycalcium soaps are obtained by carbonating a mixture of a C₇ to C₁₅carboxylic acid, which is preferably a branched chain oxo-acid in thepresence of excess calcium and a volatile solvent at a temperature from15° to 60° C. Products with basicity of 4 to 8 may be obtained. Thesepatents teach the use of saturated oxo-acids in high concentrations inthe range of 50% or more by weight, and of using mono-orpoly-substitution on carbon 3 or higher of the carboxylic acid. Thesepatents limit the percentage of acids branched on carbon 2 to between 0%and 20% by weight of the total acid.

Several unsuccessful examples have been reported wherein a highpercentage of the acid substituted on carbon 2 was used. To theknowledge of the present inventors, carboxylic acids with carbon numbersless than 7 have not been proposed for use in the preparation ofoverbased calcium soaps.

SUMMARY OF THE INVENTION

One object of the present invention is to provide shelf-stable, lightcolor liquid compositions of overbased calcium carboxylate soaps whichcomprise:

-   -   C₇ to C₂₅ saturated carboxylic acids, which are branched on        carbon 2, of between 20% to 90% by weight, and short chain        saturated carboxylic acids of between 1% to 20% by weight.

Another object of the present invention is to provide a process forpreparation of a liquid compositions of overbased calcium carboxylatesoaps includes the steps of:

-   -   (a) Preparing a mixture of aliphatic carboxylic acids which        after mixing in of the solvents contains: between 20% to 90% by        weight of C₇ to C₂₅ carboxylic acids which are branched on        carbon 2, and between 1% to 20% by weight of short chain        saturated acids, in a non-polar organic solvent, a polar organic        solvent, and an amount of calcium base sufficient to neutralize        the acids;    -   (b) neutralizing the acids in mixture with the calcium base;    -   (c) heating the acid neutralized mixture to a temperature        sufficient to evaporate water from the mixture to a dryness of        0.1% by weight water or less;    -   (d) cooling the dried calcium carboxylate mixture to a        temperature in the range of about 50° C. to 90° C.;    -   (e) overbasing cooled mixture by adding additional calcium base        dispersed in a polar organic solvent;    -   (f) carbonating the overbased mixture by bubbling carbon dioxide        gas through the mixture, and;    -   (g) heating the carbonated product at a temperature sufficient        to exporate at least part of the polar solvent and to reduce the        concentration of water in the carbonated product to a dryness of        0.1% by weight water or less.

The liquid compositions produced by this method have high clarity, lightcolor, extended shelf life and are easily filtered.

Further features and advantages of the present invention will becomeapparent from consideration of the following description and theappended claims.

DETAILED DESCRIPTION OF THE INVENTION

In a preferred embodiment of the invention, a shelf-stable, light colorliquid composition of overbased calcium carboxylate soap contains:

-   -   at least one non-polar organic solvent,    -   at least one polar organic solvent,    -   between 20% to 90% by weight of C₇ to C₂₅ saturated carboxylic        acids, which are branched on carbon 2,    -   between 1% to 20% by weight of C₂ to C₆ saturated carboxylic        acids;

The long chain saturated from C₇ to C₂₅ carboxylic acids, which arebranched on carbon 2, are preferably selected from the group consistingof 2-ethylhexanoic acid, neoheptanoic, neodecanoic acid and neononanoicacid. The most preferred long chain carboxylic acid is 2-ethylhexanoicacid.

The short chain C₂ to C₆ carboxylic acids are preferably selected fromthe group consisting of acetic acid, propionic acid, butyric acid,isobutyric acid, pentanoic acid, valeric acid, isopentanoic acid,isohexanoic acid and neohexanoic acid.

The non-polar organic solvent preferably contains at least one of thefollowing: hexane, kerosene, naphtha, benzene, toluene, ethylbenzene orxylene, or a mixture of paraffinic hydrocarbons of mineral or syntheticorigin, such as mineral spirits. Most preferably it containing a lowproportion of not more than 30% by weight of aromatic and/or naphthenichydrocarbons. This organic hydrocarbon liquid represent about 10% to 70%by weight of the total formulation.

The polar organic solvent used in the composition are preferably C₁ toC₆ alcohols,

The liquid compositions according to the present invention may containbetween about 1% to about 60% by weight of the polar organic solvent,for example methanol, 1-butanol, 2-butanol, or glycols, such as ethyleneglycol, propylene glycol, diethylene glycol, dipropylene glycol andtriethylene glycol. It also can be a glycol ether, such as ethyleneglycol monobutyl ether, diethylene glycol monobutyl ether, propyleneglycol monomethyl ether and dipropylene glycol monomethyl ether. It alsocan be a mixture of polar alcohols and/or glycols or a mixture of polaralcohols and/or glycol ethers. It also can be amines, for example,aniline, phenylenediamine, dodecylamine and mixtures thereof. It alsocan be a mixture of alcohols and/or amines, for example a mixture ofmethanol and aqueous ammonia. Most preferably the polar solvent ismethanol, glycols and/or glycol ethers. If the polar organic solventutilized is a single compound, it should preferably have a boiling pointwhich at least 120° C. When the polar organic solvent of the inventionis comprised of two or more different polar organic compounds, one ormore of those polar compounds will preferably have a boiling point whichis below 120° C. In the case of a polar organic solvent which iscomprised of multiple different polar organic compounds, it is preferredthat at least one of the compounds have a boiling point which is 120° C.or higher.

In another preferred form of the invention, a process for preparation ofa liquid compositions of overbased calcium carboxylate soap is disclosedwhich comprises the steps of:

-   -   (a) preparing a mixture of aliphatic saturated carboxylic acids        comprising: between 20% to 90% by weight of C₇ to C₂₅ saturated        carboxylic acids which are branched on carbon 2, between 1% to        20% by weight of C₂ to C₆ carboxylic acids, between 10% to 70%        by weight of a non-polar organic solvent, and between 1% to 60%        of polar organic solvent;    -   (b) dispersing an amount of calcium base sufficient to        neutralize the acids in the mixture of step (a) and neutralizing        the acids in the mixture with the calcium base;    -   (c) heating the neutralized composition at a temperature        sufficient to evaporate the water in the mixture to a dried        composition containing not more than 0.1% water;    -   (d) cooling the dried composition;    -   (e) overbasing the cooled dried composition by adding additional        calcium base dispersed in polar solvent;    -   (f) carbonating the overbased mixture by sparging carbon dioxide        gas through the mixture; and    -   (g) heating the carbonated product to remove water therefrom to        a dryness of not more than 0.1% and part of the polar solvent.

In a preferred embodiment of the process of the present invention, inabove step (b) calcium oxide and/or hydroxide with a molar equivalenceto the carboxylic acids is reacted with at least two organic saturatedcarboxylic acids at a temperature of about 40° C.-90° C., wherein one ofthe acids is a short chain acid with a carbon number ranging from C₂ toC₆ in which the short chain acid is between 1% and 20% by weight of thetotal acid. In the described preferred embodiment, the saturatedaliphatic C₇ to C₂₅ carboxylic acids, which are branched on carbon 2 arebetween 20% and 90% by weight of the total acids.

It is an important feature of the invention that the step ofneutralization be performed in the presence of at least one non-polarorganic solvent and at least one polar organic solvent.

After the neutralization step, the resulting composition is heated toabout 100° C.-150° C. to evaporate the water of neutralization. Thedried composition is then cooled to about 50° C.-90° C. and theadditional calcium oxide/hydroxide in a polar organic solvent added.

The carbonation step is then performed by sparging carbon dioxide gasthrough the reaction mixture at a temperature between 15° C. and 90° C.,and preferably between about 35° C. to about 85° C. After this step, thereaction mixture is heated to about 100° C.-50° C. to evaporate waterand possibly part of the polar solvent.

Diluents may be added, if needed. Suitable diluents are selected fromoils, aromatics, and aliphatics, but aliphatic diluents are preferred.After the second water removal step, the product is filtered.

The molar ratio of calcium base to organic carboxylic acids used in theneutralizing reaction and the overbasing steps is selected such that thebasicity index of the overbased product is greater than 1 and up to 4.

The duration of the carbonation step is preferably between 1 and 8hours, and most preferably 4 hours, and the hourly mass ratio of carbondioxide sparged to calcium hydroxide in the mixture is between 0.05 and0.5, and preferably between 0.1 and 0.4.

The long chain saturated carboxylic acids used in the this invention areC₇ to C₂₅ carboxylic acids, which are branched on carbon 2. Preferablythey are selected from the group consisting of 2-ethylhexanoic acid,neoheptanoic, neodecanoic acid and neononanoic acid.

The short chain carboxylic acids containing from 2 to 6 carbon atomsused in the invention are preferably selected from the group consistingof acetic acid, propionic acid, butyric acid, isobutyric acid, pentanoicacid, valeric acid, isopentanoic acid, isohexanoic acid and neohexanoicacid.

The non-polar organic hydrocarbon solvent used in the inventionpreferably contains at least one hydrocarbon selected from the groupconsisting of hexane, kerosene, naphtha, benzene, toluene, ethylbenzeneor xylene. It is also possible to use a mixture of paraffinichydrocarbons of mineral or synthetic origin, preferably containing a lowproportion of aromatic and/or naphthenic hydrocarbons, such as mineralspirit. The non-polar organic hydrocarbon solvent should comprise about10% to about 70% by weight of the final overbased product.

The polar organic solvent used as a promoter and possibly to enhancewater evaporation can be C₁ to C₆ alcohols, for example methanol,1-butanol and 2-butanol. It also can be a glycol, such as—ethyleneglycol, propylene glycol, diethylene glycol, dipropylene glycol andtriethylene glycol. It also can be a glycol ether, such as—ethyleneglycol monobutyl ether, diethylene glycol monobutyl ether, propyleneglycol monomethyl ether and dipropylene glycol monomethyl ether. It alsocan be a mixture of alcohols and/or glycol or a mixture of alcoholsand/or glycol ethers. It also can be amines, for example—aniline,phenylenediamine, dodecylamine and mixtures thereof. It also can be amixture of alcohols and/or amines, for example of methanol and aqueousammonia.

The preferred polar solvent is methanol, glycols and glycol ethers,which provide the highest basicities and the shortest filtration time.

A portion of the polar organic solvent is removed during the finaldrying step of the invention. The polar organic solvent will compriseabout 1% to about 60% by weight of the final overbased product.

The invention is illustrated but not limited by the following examples.

Example 1

In a flask fitted with an efficient mechanical stirrer, a Dean starkapparatus and a heating mantle, 152.24 g of a mineral spirit, 60 g ofbutyl di-glycol and 0.66 g of zinc octoate 10% were charged. 31.5 g ofcalcium hydroxide 96% was added slowly to allow its good dispersion inthe liquid. The temperature was adjusted at 60° C. at which point amixture of 86.52 g of 2-ethylhexanoic acid and 14.8 g of propionic acidwere added drop-wise over 20 min. The mixture was then heated to 140° C.over a period of 45 minutes while the water of neutralization wasdistilled off. The dried mixture was then cooled and 80 g of methanolfollowed by 45.58 g of calcium hydroxide were added. Carbon dioxideinjection was then started at a rate of 40 liters/hour for one and halfhour. After carbon dioxide injection, 40 g of methoxy propanol wasadded. The carbonated composition was then heated under a vacuum ofabout 500 mm Hg to about 700 mm Hg to a temperature of 110° C. while thewater and methanol were distilled off. The reaction product was thenfiltered by means of a vacuum pump using a filter aide. A clear stablelow viscosity product was obtained. The shelf life stability of theproduct was tested for 6 months in a closed container and proved to besatisfactory.

Example 2

Same procedures were done as the previous example but 100 g ofdi-propylene glycol mono-methyl ether were used. The reaction productwas a clear stable low viscosity product and was tested for 6 months ina closed container and again proved to be satisfactory.

Comparative Example 1

The reactor described above was charged with 180 g of 2-ethylhexanoicacid and 80 g of calcium hydroxide, and reacted with a flow of carbondioxide such that the hourly mass ratio of carbon dioxide to calciumhydroxide was 1.1 in the presence of 20.5 g of triethylene glycol, 0.75g of zinc octoate and 165 g of white mineral spirits 22.5 g of waterwere recovered from the reaction product. When the reaction ended,423.35 g of a viscous reaction mass was produced. This product could notbe filtered.

Comparative Example 2

Same composition as Example 1, except that the methanol and the wholeamount of calcium hydroxide were added from the beginning and the carbondioxide was directly injected without first removing the water ofneutralization. The final reaction product was then heated to remove thewater of neutralization. A viscous reaction mass, which could not befiltered, was obtained.

The invention claimed is:
 1. A light color, shelf-stable liquidcomposition for preparing an overbased calcium carboxylate soap having abasicity index greater than 1 and not more than 4 comprising: at leastone non-polar organic solvent, at least one polar organic solvent,between 30% and 90% by weight of C₇ to C₂₅ saturated carboxylic acidsbranched at carbon 2, and at least one C₂ to C₆ saturated carboxylicacids as a promoter.
 2. The composition for preparing an overbasedcalcium carboxylate soap of claim 1, wherein said non-polar organicsolvent is between 8% and 68% by weight of the total composition.
 3. Thecomposition for preparing an overbased calcium carboxylate soap of claim2, wherein said polar organic solvent is between 1% and 60% by weight ofthe total composition.
 4. The composition for preparing an overbasedcalcium carboxylate soap of claim 1, wherein said C₇ to C₂₅ saturatedcarboxylic acids branched at carbon 2 are selected from the groupconsisting of 2-ethylhexanoic acid, neoheptanoic, neodecanoic acid andneononanoic acid.
 5. The composition for preparing an overbased calciumcarboxylate soap of claim 1, wherein the C₇ to C₂₅ saturated carboxylicacids branched at carbon 2 comprises 2-ethylhexanoic acid.
 6. Thecomposition for preparing an overbased calcium carboxylate soap of claim1, wherein the C₂ to C₆ saturated carboxylic acids are selected from thegroup consisting of acetic acid, propionic acid, butyric acid,isobutyric acid, pentanoic acid, valeric acid, isopentanoic acid,isohexanoic acid and neohexanoic acid.
 7. The composition for preparingan overbased calcium carboxylate soap of claim 1, wherein said polarorganic solvent comprises a mixture of at least one alcohol and at leastone glycol or glycol ether.
 8. The composition for preparing anoverbased calcium carboxylate soap of claim, 1, wherein said C₂ toC₆saturated carboxylic acid is between 1% and 20% by weight of the totalcomposition.
 9. A light color, shelf-stable liquid composition forpreparing an overbased calcium carboxylate soap having a basicity indexgreater than 1 and not more than 4, comprising: at least one non-polarorganic solvent at least one polar organic solvent between 25% and 90%by weight of C₇ to C₂₅ saturated carboxylic acids branched at carbon 2,and between 1% to 20% by weight of C₂ to C₆ saturated carboxylic acids.